1. Field of the Invention
The present invention relates to an illuminator, and a spectral apparatus and an image reading apparatus, in which the illuminator is used. Particularly, the invention relates to an illuminator that suitably guides a light beam from a light source unit with a light guiding member to illuminate an illumination object (original).
2. Description of the Related Art
Conventionally, in an illuminator such as an LCD backlight in which a low profile and uniform illuminance are required, there is proposed an illuminator that guides the light beam from the light source unit with the light guiding member to illuminate the illumination object (for example, see Japanese Patent Application Laid-Open No. 2000-137218).
There is proposed an illuminator in which the light guiding member, in which a shape of an incident surface to which the light beam is incident from the light source unit is changed, is used in order to enhance efficiency of a taking light quantity when the LED is used as the light source (for example, see Japanese Patent Application Laid-Open No. 2005-265752).
Japanese Patent Application Laid-Open No. 2000-137218 discloses an LCD backlight structure in which a reflector plate and a light taking surface are provided. The reflector plate reflects the light beam emitted from the light source. In the light taking surface, a side end face of a light induction plate is enlarged and largely extended to a side face of the light source to take a large amount of light beams. A thickness of the light induction plate except the light taking surface is decreased.
As to an illuminator that illuminates an image having color information in a spectral apparatus that obtains the color information, there is well known an illuminator that illuminates the illumination object with the light beam from the LED while the LED is disposed toward the illumination object instead of guiding the light beam from a xenon lamp through an optical fiber.
Japanese Patent Application Laid-Open No. 2005-265752 discloses a technique in which a sample image is illuminated with the light beam from the LED while the LED is inclined by 45 degrees with respect to the sample image.
Because the illuminator disclosed in Japanese Patent Application Laid-Open No. 2000-137218 is formed for the LCD backlight, the position of the illuminated surface does not vary. However, unfortunately illuminance is changed when the position in the thickness direction of the illuminated surface varies. In the disposition of the LED of Japanese Patent Application Laid-Open No. 2000-137218, because the light beam in the direction of the highest light intensity is substantially horizontally incident to the illuminated surface, the increase in illuminance is not expected in the illuminated surface.
In the illuminator disclosed in Japanese Patent Application Laid-Open No. 2005-265752, the LED is disposed in order to increase the illuminance while inclined by 45 degrees with respect to the sample image (illuminated surface). Therefore, the illuminance is largely changed when the position of the illuminated surface varies. Further, because the LED is inclined, it is necessary to incline the board retaining the LED, which results in a problem that an illumination unit is enlarged.